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188 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

Another heterocyclic compound obtainable in considerable quantities-quin-

oline-nitrates in the isocyclic ring. Indole and carbazole behave in a similar way.

Nitro derivatives of these compounds have not yet found practical application.

Dinitro derivatives of thiophene described by Steinkopf have recently been

obtained in a pure form by Blatt and co-workers [80] by nitrating 2- and 3-nitro-

thiophenes in nitric acid-acetic anhydride mixture, according to Steinkopf. A good

yield of 2,4-dinitrothiophene (m.p. 49-50°C) was obtained. In the case of nitrating

3-nitrothiophene a smaller proportion of 2,5-dinitrothiophene (m.p. 78-82°C)

was also formed.

The ability of the substances of being nitrated depends on many factors which

exercise their influence upon the activity of the compounds. For example cyclo-

pentadiene, C 5 H 6 can readily be nitrated with ethyl nitrate (Thiele [72]). Titov [73]

explained this fact by suggesting that the hydrocarbon forms readily the anion C 5 H 5 -

which possesses a high potential π.

On the contrary, ferrocene, (C 5 H 5 ) 2 Fe, can be nitrated with difficulty. This is

explained by formation of cation (C 5 H 5 ) 2 Fe+ with reduced activity towards electro-

philic agents.

NITRO COMPOUNDS AS EXPLOSIVES

Among aliphatic nitro compounds nitromethane was only recently recognized

as an explosive. Tetranitromethane is not explosive but can form an explosive when

mixed with combustible substances. Tetranitromethane possesses here a character

of an oxygen carrier.

Nitro derivatives of aromatic compounds as explosives are of greatest practical

importance.

It is usually considered that only those nitro compounds possess explosive

properties which contain at least two nitro groups attached to one benzene ring.

However, Berthclot [81] noticed as long ago as 1887 that the presence of even one

nitro group is sufficient to increase the ease of thermal decomposition of the aromatic

compound. This was later confirmed by Datta and Chatterjee [82], and Condit and

Haynor [83] when studying the temperatures of thermal decomposition of nitro

compounds. Nevertheless, among aromatic nitro compounds only those which

have three or more nitro groups for one benzene ring (and some of those which

have two) exhibit distinctly marked explosive properties. Among the compounds

with two nitro groups, only dinitrobenzenes and dinitrotoluenes are recognized

as explosives while dinitronaphthalenes are on the borderline between explosive

and non-explosive substances. Trinitronaphthalene has explosive properties similar

to those of dinitrobenzene, since the ratio between the number of nitro groups

and carbon atoms is approximately the same for both compounds.

For this reason, mononitro compounds will be described only from the view-

point of their utilization as intermediates for the preparation of higher nitrated
products.